Anatomy - Week 7/8 PP Flashcards
Types of Tooth Tissues
Enamel
Dentin
Pulp
Cementum
Enamel
hardest structure in our bodies - harder than bone
-originates from the ectoderm
-formed by ameloblasts
-not a living tissue (mature enamel does not contain cells that are capable of repair and regeneration, no blood supply or nerves)
-It is permeable - allows for the exchange of ions, allows for demineralization & remineralization
-composed of inorganic (mineral) and organic substances
Preservation of Enamel
- Preservation is the goal of dental health professionals
-Consider properties & histology
*determining caries risk
*counselling patients/communities on fluoride use
*Application of sealants and restorations
*use of the correct polishing and toothpaste agents
Mature enamel composition
Approximately 96% inorganic materials and 1% organic
materials (1%) and water (3%)
Main mineral component
Calcium hydroxyapatite
§ Found in lesser extents in dentin, cementum and bone
§ Appears more radiopaque on a radiograph
◦ Other minerals also present in smaller amounts
* Carbonate, magnesium, potassium, sodium and fluoride
Thickness of Enamel
A thick as 2.6mm at cusps of molar teeth
-thinner at incisal edgers
Color of enamel
-Translucent
* Colour varies
* yellowish to grayish/bluish white
* Varies with age
* Primary teeth
* Whiter
* More opaque crystalline form
* Permanent teeth
* Yellowish-white to gray
* Reflects underlying dentin
Macroscopic Structure
Appears Hard, shiny & Translucent
Histology of Enamel
Lines of Retzius - Incremental lines - represent the deposition of enamel during the formation of a tooth
Hunter-Schreger bands - alternating light and dark bands - caused by enamel prisms changing direction
Enamel is composed of…
Enamel Rods also known as enamel prisms
* Crystalline structural unit of enamel
* Extend from the surface of the tooth to the DEJ
* Grouped in rows and organized around the
circumference of the long axis of the tooth
* Rows are generally perpendicular to the surface of the tooth
Enamel Rod Structure
-Rod Sheath
*covering of the enamel rod
*acid resistant (hardest enamel structure)
-Inter-rod substance (interprismatic substance)
*the material between the keyhole shaped enamel rods
*like a cement or glue
How do you think the arrangement of the enamel rods influences the penetration of decay? Do you think the rate of decay slows or increases once it reaches the dentin?
Penetration of decay follows the pattern of the rods
Decay will increase once it reaches the dentin as it is less mineralized
What are Enamel Lamellae?
Enamel lamellae are partially mineralized vertical sheets of
enamel matrix that extend from the DEJ near the tooth’s cervix to the outer occlusal surface
What are Enamel Tufts?
Enamel Tufts are noted as small, dark brushes with their bases near the DEJ
Enamel Spindles
They represent short dentinal
tubules near the DEJ junction.
* odontoblasts that crossed the basement membrane before it
mineralized into the DEJ.
* dentinal tubules become trapped
during the appositional growth of
enamel matrix, which becomes
mineralized around them.
* Clinical implications of enamel
spindles are unknown at this
time (
Abfraction
Enamel can also be lost as a result of abfraction. Abfraction is thought to be caused by tensile and compressive forces during tooth flexure, which possibly occurs during parafunctional habits with their occlusal loading
Clenching & grinding
happens only on cervical 1/3 of tooth
Parafunctional habit ^
Attrition is..
the wearing away of hard tissue as a result of tooth-to-tooth contact.
Abrasion is..
is the wearing away of tooth surface caused by friction or a mechanical process. Abrasion happens when teeth are brushed too vigorously in sweeping horizontal strokes. The use of a hard toothbrush can also cause the problem.
Erosion is..
This can happen with bulimia and gastric reflux as well as overusing acidic drinks (even in baby bottles) or foods
*meth mouth is a type
Lemon water is another cause
Dentin is..
- makes up bulk of tooth
-not clinically visible
*usually covered by enamel or cementum (exceptions - attrition or abrasion of enamel or cementum)
Dentin Origin
Dental papilla > mesenchyme cells
Dentin - living tissue?
Odontoblasts (dentin producing cells) are present throughout life of a tooth to continuously produce dentin
Dentin Calcification
Softer than enamel (less calcified)
◦ More flexible than enamel
§ Less mineralized - more radiolucent on a radiograph
Dentin Composition
Inorganic Substance (hydroxyapatite crystals) - 70 %
Organic substance (proteins) - 20%
Water - 10%
Dentin appearance
Resemblance to Bone
◦ Harder than bone and cementum
§ Resembles bone in physical and chemical properties
Colour of Dentin
Yellow
§ Clinical color of a tooth – can be seen through translucency of enamel